腾冲HCO_3-Na型热泉水的化学模型  

The Chemical Model of Thermal Spring Water of HCO_3-Na Type, Tengchong

作　　者：过帼颖 殷纯嘏[1] 

机构地区：[1]北京大学地质学系

出　　处：《北京大学学报（自然科学版）》1990年第6期700-710,共11页Acta Scientiarum Naturalium Universitatis Pekinensis

基　　金：国家自然科学基金委员会;国家教育委员会科学基金

摘　　要：腾冲的热泉大部分是BCO_3-Na型水。根据Na^+、HCO_3^-含量对数相关图和Na^+、SiO_2含量半对数相关图可将HCO_3-Na型水分成4组,第4组HCO_3-CO_3-Na或CO_3-HCO_3-Na型水在组成上同第1组。 第1、4组热泉水的化学组分主要是Na^+、H^+和H_4SiO_4。化学热力学计算结果表明它们是钠长石在富含CO_2气体的60℃热水中异成分溶解产物。 第2组的水化学组分比第1组有较高的Ca^(2+)含量,它是钙长石在富含CO_2气体的100℃左右热水中异成分溶解的结果。 第3组的水化学组分有较高的Na^+、K^+和Ca^(2+)含量,K^+从热泉水围岩中迁移出来,表明该类水热系统的水热蚀变较深,可能有较高的热储温度。The water of HCO3-Na type which are divided into four groups based on the related logarithm maps of Na+ versus HCO3- contents and Na+ versus SiO2 contents is the most common species in Tengchong thermal spring waters. The water of HCO3-CO3-Na type and CO3-HCO3-Na type as the fourth groups are similar to that of the first group HCO3-Na type in origin.The major ions of the first and the fourth group result from the dissolution of albite that is strongly influenced by the chemically aggressive nature of the water caused by dissolved CO2 at 60℃. The chemical composition of the thermal spring water expressed in terms of Na+,H+ and H<SiO4 is plotted in the kaolinite, Na-montmoril-lonite or low-albite stability field in Fig. 6, respectively. It is possible from athermo-dynamic viewpoint that albite is dissolved early incongruently and kaolinite,H4SiO4 and Na+ are produced. As the dissolution continues H4SiO4 and pH increase further and the water composition moves through the kaolinite field into the Na-montmorillonite stability field or moves directly toward the low-albite. When the composition evolues to the boundary of low-albite field, equilibrium with respect to the albite is attained.More Ca2+ is characteristic of the thermal spring water as the second group than the first group. It is results from the dissolution of plagioclase feldspar in the water at 100℃ with abundant CO2. The water composition involved H4SiO4, Ca2+ Na+ and EP is plotted in the leonhardite field. The leonhardite is in equilibrium or near equilibrium with the water composition.In the geothermal systems of the thermal spring water of the third group HCO3-Na type most of the country rocks are gneiss quartzite and some sedimentary rocks. The thermal spring water contains higher Na+, K+ and Ca2+ contents. Moving out of the rocks for potassium ion expresses higher hydrethermal alteration for these thermal spring water which probably have higher geothermal reservoir temperature.

关 键 词：热泉水 化学反应模型 化学热力学 

分 类 号：P314[天文地球—固体地球物理学]